Often a website which hosts videos will have a common top-level page that groups conceptually related videos together. Such a page may be of interest to a user searching on that subject. Sites with many videos about a single subject can group these videos together on a top-level page, often known as a gallery. This can make it easier for users to find exactly what they're looking for. In this case, you can use a Sitemap to tell Google the URL of the gallery page on which each video appears.

You can specify the URL of the gallery level page using the optional tag <video:gallery_loc> on a per-video basis. Note that only one gallery_loc is allowed per video.